You wanted to approach conversion of data like emails, appointments, tasks, journals, to do list, addresses from Outlook PST to Lotus Notes with some highly experienced outside application. Outlook to Notes which has long term experience in successful data migration.
Alternate solution: There is a method via which you can move Outlook email to Lotus Notes, but we never recommend you to use this method. This is popular as manual method. This process involves high labour from your side. You have to wait for one file transfer and then get on with another, thus the process goes on and on. The condition where the matter is of bulk data migration, this solution is not successful. It is tedious task and annoying task for you.